Erwin E, Miller K D
Department of Physiology, University of California, San Francisco, California 94143-0444, USA.
J Neurosci. 1998 Dec 1;18(23):9870-95. doi: 10.1523/JNEUROSCI.18-23-09870.1998.
We extend previous models for separate development of ocular dominance and orientation selectivity in cortical layer 4 by exploring conditions permitting combined organization of both properties. These conditions are expressed in terms of functions describing the degree of correlation in the firing of two inputs from the lateral geniculate nucleus (LGN), as a function of their retinotopic separation and their "type" (ON center or OFF center and left eye or right eye). The development of ocular dominance requires that the correlations of an input with other inputs of the same eye be stronger than or equal to its correlations with inputs of the opposite eye and strictly stronger at small retinotopic separations. This must be true after summing correlations with inputs of both center types. The development of orientation-selective simple cells requires that (1) an input's correlations with other inputs of the same center type be stronger than its correlations with inputs of the opposite center type at small retinotopic separation; and (2) this relationship reverse at larger retinotopic separations within an arbor radius (the radius over which LGN cells can project to a common cortical point). This must be true after summing correlations with inputs serving both eyes. For orientations to become matched in the two eyes, correlated activity within the receptive fields must be maximized by specific between-eye alignments of ON and OFF subregions. Thus the correlations between the eyes must differ depending on center type, and this difference must vary with retinotopic separation within an arbor radius. These principles are satisfied by a wide class of correlation functions. Combined development of ocularly matched orientation maps and ocular dominance maps can be achieved either simultaneously or sequentially. In the latter case, the model can produce a correlation between the locations of orientation map singularities and local ocular dominance peaks similar to that observed physiologically. The model's main prediction is that the above correlations should exist among inputs to cortical layer 4 simple cells before vision. In addition, mature simple cells are predicted to have certain relationships between the locations of the ON and OFF subregions of the left and right eyes' receptive fields.
我们通过探索允许两种特性联合组织的条件，扩展了之前关于皮层第4层眼优势和方向选择性独立发展的模型。这些条件通过描述外侧膝状体核（LGN）两个输入的放电相关性程度的函数来表达，该函数是它们视网膜拓扑分离和“类型”（ON中心或OFF中心以及左眼或右眼）的函数。眼优势的发展要求一个输入与同一只眼睛的其他输入的相关性强于或等于其与另一只眼睛输入的相关性，并且在小视网膜拓扑分离时严格更强。在将与两种中心类型的输入的相关性相加之后，这一点必须成立。方向选择性简单细胞的发展要求：（1）在小视网膜拓扑分离时，一个输入与相同中心类型的其他输入的相关性强于其与相反中心类型输入的相关性；（2）在树突半径（LGN细胞可以投射到共同皮层点的半径）内较大的视网膜拓扑分离时，这种关系反转。在将与两只眼睛的输入的相关性相加之后，这一点必须成立。为了使两只眼睛中的方向匹配，感受野内的相关活动必须通过ON和OFF子区域的特定眼间对齐来最大化。因此，两只眼睛之间的相关性必须根据中心类型而不同，并且这种差异必须在树突半径内随视网膜拓扑分离而变化。这些原则由一大类相关函数满足。眼匹配方向图和眼优势图的联合发展可以同时或顺序实现。在后一种情况下，该模型可以在方向图奇点位置和局部眼优势峰值之间产生类似于生理观察到的相关性。该模型的主要预测是，上述相关性应该在视觉之前皮层第4层简单细胞的输入之间存在。此外，预测成熟的简单细胞在左眼和右眼感受野的ON和OFF子区域位置之间具有某些关系。
